


brother mine

by m3owww



Series: maribat [16]
Category: Batman - All Media Types, Maribat - Fandom, Miraculous Ladybug
Genre: Bruce Wayne is Overdramatic, Bruce Wayne is So Done, Bruce Wayne's punk phase, Crack, Dick Grayson Loves His Cereal, Fluff, Humor, Marinette's the cool aunt now, hmm, mari is bruce's older sister, now with a part 2!, oh nO I FORGOT ABOUT JASON FOR THE ENDING AAAAAA, oh what a wonderful life she lives, she breaks through their security purely for big sis privileges of embarrassing the batman, this might become a thing where i just update it whenever, wait gonna make that into its own thing dON'T WORRY
Language: English
Status: Completed
Published: 2020-12-14
Updated: 2020-12-15
Packaged: 2021-03-11 01:40:47
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 2
Words: 2,047
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/28077123
Author URL: https://archiveofourown.org/users/m3owww/pseuds/m3owww
Summary: Anon: This isn't exactly a fic, but more of a one shot. What if Batman walked in on Big Sis Mari, telling the JL embarrassing moments and stories about kid Bruce, and the JL is like you sure that's the same person? Cause maybe tiny Bruce was just like the most over the top person---------------But the main hall is somehow empty, and despite the numerous times he’s wished for just a moment of peace and quiet, Batman doesn’t have a good feeling about it.He hears voices from the briefing room, and slinks forward with silent steps, a hand going to his utility belt and drawing out a batarang, just in case.As he gets closer, the voices become clearer, and-was that laughter?
Relationships: Batfamily Members & Marinette Dupain-Cheng | Ladybug, Bruce Wayne & His Infinite Amount of Children, Justice League & Bruce Wayne, Marinette Dupain-Cheng | Ladybug & Bruce Wayne
Series: maribat [16]
Series URL: https://archiveofourown.org/series/1842979
Comments: 42
Kudos: 377





	1. Chapter 1

**Author's Note:**

> hi! I'm alive! and I have a shit ton of things to do and yet I'm still doing this instead of actually tackling my five thousand homework assignments because I am a master procrastinator.
> 
> also, please don't murder me for any errors, I wrote this in fifteen minutes. yeet.

_ Recognized: Batman, 0-2, _ The mechanical voice of the zeta tube drones, and Batman steps out of the teleporter with a dramatic swish of his cape.

His first thought is that the main hall of the Watchtower is eerily empty. 

There’s always at least one hero lurking in the large, open space, whether it be Barry helping himself to the food in the fridge, Hal watching TV in the lounge area, Victor on monitor duty, or Diana doing pushups on the ground, usually with at least two Leaguers sitting on her back as she does them.

But the main hall is somehow empty, and despite the numerous times he’s wished for just a moment of peace and quiet, Batman doesn’t have a good feeling about it.

He hears voices from the briefing room, and slinks forward with silent steps, a hand going to his utility belt and drawing out a batarang, just in case. 

As he gets closer, the voices become clearer, and- was that  _ laughter? _

Yep. That was definitely Clark’s cackle, mixed in with Diana’s melodious laugh and  _ what is going on? _

Batman pushes open the door to the briefing room and freezes once he sees the person that has the League in tears, hunched over and clutching their stomachs as their shoulders shake with genuine laughter, so different from the ones ripped from the throats of Joker victims.

And there’s one more person, dressed in red-

“No,” Batman growls. “No, you did not.”

Ladybug casually sits on the massive table in the middle of the room, looking utterly at ease. The red and black spotted wings on her back flutter, which indicates that she’s in an extremely good mood. 

She turns around at the sound of his voice and her face splits into an even wider grin, beaming as she gives him a cheerful wave.

“Hello, little brother dearest!” She greets happily, like she hasn’t just shattered his entire reputation. “How have you been?”

Batman opens his mouth to reply with something witty, but he doesn’t get a chance before Diana cuts him off. 

“Batman,” She wheezes, brown eyes sparkling with mirth. “Did you really have a punk phase?”

“I don’t really see what’s funny about it,” Batman grumbles. “Every teen has a rebel phase at some time or another.”

“Yeah, but you went and got high. And then- And then-” Clark can’t even finish his sentence because he’s laughing so hard. Batman wants to crawl into a hole and not come out for maybe the next hundred years.

“He got high,” Ladybug grins, blue eyes teasing. “And then he started crying about how snakes had no legs for three hours and called bread ‘raw toast’. Multiple times.” 

That sends another peal of laughter through the group, and Batman wonders if the League would be opposed to him throttling his older sister.

“Ladybug. How did you get into the Watchtower?” He asks, trying to salvage the last shreds of his dignity. Batman doesn’t remember ever giving her a zeta designation.

Ladybug scoffs, waving a hand. “Pfft, like your satellite being in space could stop the Guardian of the Miraculi. Meet Kaalki.”

A small, horse-like kwami floats out from a hidden pocket in Ladybug’s suit and looks him up and down for a moment before turning her nose up, away from him, and sniffing haughtily.

Did she just decide The Batman himself was not worth her time? Yes, she did.

Batman doesn’t really know how to feel about that.

Ladybug pulls out her yoyo and flips it open, pretending to dramatically gasp. “Oh goodness! Look at the time! I must get back to Paris, it’s getting late over there.” She gracefully slides off the table, and in the same motion, stands up on her toes to kiss him on the cheek.

“Bye, little brother! Don’t get into too much trouble!” She calls, grinning, before saying “Kaalki, full gallop!” and hopping through a portal, which closes after her and makes it seem like she’s never really been there at all.

Batman would have believed it, too, if it wasn’t for the room full of the world’s most powerful heroes still laughing behind him.


	2. Chapter 2

**Summary for the Chapter:**

> Anon: I recently read your platonic brucinette post, it was amazing, i couldn't stop laughing. What if she invites herself over to the Manor or something and the boys have no idea who she is (cause I feel like he wouldn't mention her cause she would probably ruin his reputation even more since his kids would probably spread the stories to their own friends) but I feel like maybe Tim already know her since he was in Paris looking for Bruce (when he got "killed" by Darkseid), he would probably see her as a mom or fun aunt that he could vent to

**Notes for the Chapter:**

> there was not going to be a part two, but someone asked, so I was obliged to write it.

Dick Grayson had seen a lot of unexpected things throughout his lifetime, but he really did not expect to come downstairs for a nice bowl of cereal for breakfast and find a woman who looked eerily like the late Martha Wayne sitting at the table and eating his Bat Puffs.

Wait.

“Those are my Bat Puffs!” Dick shrieks, because he has priorities. That’s the last of his cereal, okay? And it’s going to be two days before Alfred goes on his next grocery run and he’s really bad at shopping for food on his own. Sue him.

Not-Or-Maybe-Possibly-If-You-Believe-Conspiracy-Theories-Martha-Wayne simply laughs, and easily dances out of the way of his grab for the bowl, moving out of his reach with an elegance and grace that can only mean she spends part of her day dressed in a different costume. Whether or not she was a good guy still remained to be seen, considering she had somehow broken into the Manor without setting a single alarm off and was currently eating the last of his Bat Puffs. 

A truly despicable act, indeed.

“Grayson?” Damian chooses that exact moment to come down the stairs. “I heard you scream. What’s-” He snarls the moment he catches sight of Not-Martha-Wayne, pulling out a knife from somewhere in the folds of his pajamas and hurling it at her head with impressive speed and accuracy.

Not-Martha-Wayne simply ducks, letting the knife thud into the wall behind her, making Dick wince. Alfred was not going to be happy.

“Identify yourself, woman!” Damian screeches, pulling out another knife. “Who are you, and how did you get in here?”

Not-Martha-Wayne tilts her head, blue eyes sparkling with mirth. “Really? I’m not even allowed to eat cereal in my own home now?”

Dick is slowly growing more and more convinced that Not-Martha-Wayne is actually Zombie-Martha-Wayne.

Damian freezes, eyeing her suspiciously. “Your home?”

“Wh’s goin’ on?” Tim slurs, stumbling down the stairs. “Why ‘re you all screamin’?”

Maybe-Zombie-Martha-Wayne brightens when she sees Tim. “Timber! How’s it going?”

Tim rubs his eyes, once, twice, and then his face splits into a grin when he finally registers Maybe-Zombie-Martha-Wayne’s presence. “Marinette! It’s so good to see you!”

And  _ okay, what. _

Tim hurries down the stairs (meaning only marginally faster than before, he hasn’t had his morning coffee yet,) and ignores the coffee machine in favor of hugging Possibly-Undead-Martha-Wayne, who laughs and puts down the bowl of Bat Puffs in favor of hugging him back. Dick takes the opportunity to snatch the bowl away from her, mourning the fact that there’s only a bit of milk left at the bottom of the bowl.

“Good to see you too, Tim,” Not-Martha-Wayne, whose name is apparently Marinette (why does that sound familiar?) ruffles Tim’s hair. “It’s been a while, hasn’t it?”

“Tim,” Dick says, at the same time Damian demands “Drake.”

“How do you know this woman?” They say at the same time (Dick stubbornly ignores that Damian replaced ‘woman’ with ‘harlot’).

“You mean you don’t?” Tim asks, frowning. “She’s-”

“Marinette,” Bruce cuts Tim off, having appeared at the foot of the stairs in his usual dramatic fashion. 

Not-Martha-Wayne-But-Still-Really-Looks-Like-Her-Whose-Name-Is-Apparently-Marinette beams and waves cheerfully at Bruce, who looks done with life. “Hey, little brother! I see you haven’t gotten tired of dressing up as a giant bat to beat people up yet!”

Well, that was a lot to unpack. Dick decided he’d start with the easiest thing.

“Little brother?” He looks from Marinette to Bruce, Bruce to Marinette, noting the resemblance in both of them to Thomas and Martha Wayne. “You mean-  _ she’s your older sister? _ ” Dick shrieks, turning to Bruce. “Why have we never heard about her?”

“Really, Bruce?” Marinette gasps, mockingly placing a hand over her heart. “I’m devastated. How could you, after everything we’ve been through, not even tell your hundred thousand children that I even  _ exist _ ?”

Bruce doesn’t reply, instead letting out one long sigh through his nose.  _ Huh. Sixteen whole seconds. Impressive. _

“Just kidding,” Marinette grins once Bruce has finally stopped sighing. “He’s never told you because I travel the world a lot, my job is super dangerous, and because I’d expose all his deepest, darkest secrets.”

“Like his greatest fears?” Damian asks. Cass, who had silently entered the kitchen at some point or another, stood behind him, ready just in case he pulled out another knife.

Marinette tilts her head. “What? No!” Like how he wiped off one of the eyebrows on Sylvia McCartney’s face when he was four-”

She doesn’t get to finish that sentence because Bruce has made a mad dash across the kitchen, evidently aiming to get her to stay quiet. Marinette dances out of his hold with a giggle and continues speaking even as Bruce chases her all around the kitchen.

“-anyway, he declared that ‘she had something on her face’, wiped off one of her drawn-on eyebrows-” She ducks underneath a plate, which Cass deftly catches before it hits the wall. “-and then went ‘There. I got it for you!’”

A shoe flies at her head. Marinette bats it away with one hand. 

Dick tries valiantly to stifle his snickers, but judging by the evil eye Bruce is giving him, it’s not quite working.

“And there was that time we were at that four-star restaurant in Star City and he ate too much and-” Marinette raises an eyebrow as she catches a toaster in her hands. “Really now, Bruce? A toaster? You know it’ll take more than that to stop me. So he ate too much and got a stomach ache, then started holding his torso and very loudly declaring that he was starting his period.”

Dick doesn’t even bother holding in the laughter this time, and neither do any of his siblings. If only Jason was here to see this, but alas, he was at his own apartment and had no clue that this was going on. Neither did Steph, for that matter, and Duke was already out on patrol since he was somehow a morning person. What a travesty.

“And then there was that time when-” Marinette is cut off by another one of Bruce’s long, very drawn-out sighs. 

“Look, Mari, I think they get the point,” He groans (well - as close to groaning as the Batman ever got), pinching the bridge of his nose. “You can stop now.”

“Oh, you’re just annoyed that you couldn’t stop me,” Marinette retorts with yet another smile, and Dick is once again struck by how similar she looks to the lady in the portrait that hangs over the fireplace in the largest of the Manor’s three living rooms. “I suppose you’re right, however. Despite the abundance of embarrassing stories, they do run out at some point, and I’d prefer not to use them all up in one go, ya know? I have to be the cool aunt. Kate can keep wine aunt, but I’m the cool one now.”

“I think Miss Katherine might disagree with that,” Alfred says mildly. “However, I do believe you can win the children over if you tell them about the time your father brought Master Bruce to his board meeting.”

The look of utter betrayal Bruce gives Alfred makes them crack up all over again.

\--o0o--

“Man, I am so glad you got it all on camera,” Duke grins, placing two bowls of popcorn on the coffee table before flopping back down onto the couch. “This is going to be great.”

Tim waves a hand dismissively. “I just hacked the cameras in the Manor. Bruce’s paranoia backfired this time.”

Steph cheers and immediately makes a grab for the popcorn as Cass hits the play button on the remote, and Dick can’t help but crack a smile at his own face when he sees the last of his cereal being eaten.

“Richard, I find it concerning that your first thought was of your cereal and not the intruder,” Damian observes.

Dick ruffles his hair, drawing out a squawk of protest. “Well, what can I say? I really like Bat Puffs.”

The Wayne siblings settle down for a movie night that is definitely going to be filled with lots of laughter.

**Author's Note:**

> hit me up on [tumblr](https://m3owww.tumblr.com/) if you wanna yell at me, yell with me, talk to me, send a fic request, or anything, really.


End file.
